As shown in FIG. 8, a conventional loudspeaker includes magnetic circuit 1A, voice coil 2A, diaphragm 3A, edge 4A, frame 5A, suspension holder 6A, and edge 7A. Voice coil 2A is disposed in a gap in magnetic circuit 1A so as to be able to vibrate freely in the gap and is connected to the inner rim of diaphragm 3A. Frame 5A is connected to the outer rim of diaphragm 3A via edge 4A. Suspension holder 6A is disposed on the rear surface of diaphragm 3A. Edge 7A connects frame 5A and suspension holder 6A. Edges 4A and 7A protrude in opposite directions to each other so as to make the vertical excursion of diaphragm 3A symmetrical to each other, thereby reducing the distortion of the loudspeaker. A well-known conventional example of the present invention is described in Patent Document 1 shown below.
The loudspeaker shown in FIG. 8 is weighty due to the weight of suspension holder 6A, which is used to securely support diaphragm 3A. The large weight does not matter very much for a bass loudspeaker which requires a large output, but causes a reduction of driving efficiency for a mid/high-range loudspeaker.
Patent Document 1: Japanese Patent Unexamined Publication No. 2004-7332